Please take a look at @EstherSchindler answer to this question.
Is there any reason why she should not post the URL to her eBook? I for one would like to read it, if she is agreeable, and I think that it would help others. I can see no harm in doing so ...
Here are some relevant links:
From the accepted answer to "How can I link to an external resource in a community-friendly way?"
- you paraphrase the content of the linked item (possibly omitting details or examples)
- you identify the author (yourself, MSDN, etc)
- someone could benefit from the answer without reading the linked item at all
- you include information to let the reader decide if clicking the link is worthwhile
The FAQ on What makes something spam and when should I flag it?
A post should be marked as spam only if it advertises a product, service, or similar and is unsolicited or lacks disclosure.
And, since Esther discloses her affiliation, I just quote the part about Unsolicited:
- Unsolicited means that mentioning the product serves no purpose other than promotion. For example, if an answer mentions a software that may solve the asker’s problem or a question about web programming references a website as an example, this is not unsolicited (it may still be spam if there is an undisclosed affiliation).
In addition, here is a relevant answer from TWP Meta itself.
If the answer meets these requirements after the link was included, it would be okay.
